1. Field of Invention
The invention relates to a system and method for representing compressed information within a data stream.
2. Description of Related Art
Currently, numerous standards exist for encoding data for transmission across a channel to a receiver (decoder). For example, the International Standard ISO/IEC 13818-7, Advanced Audio Coding, also known as MPEG-2 AAC, specifies a syntax for representing compressed audio signals which are suitable for transmission over limited bandwidth channels. The same syntax with one minor backwards compatible extension is International Standard ISO/IEC 14496-3, also known as MPEG-4 audio. Because these standards typically address transmission of the compressed data over bit-serial channels (e.g., a radio modem channel) the compressed format is often referred to as a bitstream, although the standard is equally valid for other transmissions or storage formats.
Current standards for representing compressed data in a data stream may not support re-synchronization of the bitstream and a decoder. Additionally, current standards may not provide for any explicit form of error detection, error control, or error recovery. For example with existing protocols, such as MPEG-2 AAC, it is necessary for the decoder to know the beginning of a received stream of raw data in order for the decoder to be able to decode the raw data. While information for synchronization of a decoder to a raw data stream is available in applications, such as receiving a computer file from a hard drive or the like, in many applications the synchronization information is not available. For example, in satellite or digital radio communications, the decoder can begin to receive the signal at any point during the signal transmission. Accordingly, the decoder needs to be able to synchronize with the signal in order to properly decode the signal.
One solution to resolving the synchronization problem, is to provide a separate synchronization channel in parallel to the data channel. An example of this technique could include having a decoder receive a first data stream containing video data, a second data stream containing audio data and a third data stream containing synchronization data. Accordingly, the decoder may then use the synchronization data to decode and synchronize with both the audio and video data. However, such systems can become very complicated since the decoder must receive and process numerous different signals.
Accordingly, there exists a need for providing a method for representing compressed information which provides for re-synchronization along with error detection and error correction.